Abstract: Jerry Fodor has consistently cited the persistence of illusions--especially the Müller-Lyer illusion--as a principal form of evidence for the informational encapsulation of modular input systems. Fodor proposed that these modules' stereotypical deliverances about how the world appears could serve as a theory-neutral observational foundation for (scientific) knowledge. For a variety of reasons Fodor rejected Paul Churchland's putative counter-examples to these mental modules' cognitive impenetrability. Fodor's discussions suggest that demonstrating modules' cognitive penetrability would hinge on showing that because subjects either (a) acquire some explicit theory or (b) gain wider perceptual experience, they would, in the synchronic case, very quickly cease to experience the illusion or, at any rate, experience a mitigated version of it. Diachronic penetration, by contrast, would involve processes that deliver one of these outcomes over a decidedly longer period. Marshall Segall, Donald Campbell, and Melville Herskovits' (1966) research across seventeen cultures shows that culturally influenced differences in visual experience during the first two decades of life substantially affect how people experience the Müller-Lyer stimuli. In some of the societies most people were virtually immune to the illusion. Such findings call Fodor's showcase evidence for the cognitive impenetrability of the visual input system into question and, thereby, threaten to block the path to the theory-neutral, observational consensus that he scouts

Abstract: Although the study of visual perception has made more progress in the past 40 years than any other area of cognitive science, there remain major disagreements as to how closely vision is tied to general cognition. This paper sets out some of the arguments for both sides (arguments from computer vision, neuroscience, Psychophysics, perceptual learning and other areas of vision science) and defends the position that an important part of visual perception, which may be called early vision or just vision, is prohibited from accessing relevant expectations, knowledge and utilities - in other words it is cognitively impenetrable. That part of vision is complex and articulated and provides a representation of the 3-D surfaces of objects sufficient to serve as an index into memory, with somewhat different outputs being made available to other systems such as those dealing with motor control. The paper also addresses certain conceptual and methodological issues, including the use of signal detection theory and event-related potentials to assess cognitive penetration of vision. A distinction is made among several stages in visual processing. These include, in addition to the inflexible early-vision stage, a pre-perceptual attention allocation stage and a post-perceptual evaluation, memory-accessing, and inference stage which provide several different highly constrained ways in which cognition can affect the outcome of visual perception. The paper discusses arguments that have been presented in both computer vision and psychology showing that vision is "intelligent" and involves elements of problem solving". It is suggested that these cases do not show cognitive penetration, but rather they show that certain natural constraints on interpretation, concerned primarily with optical and geometrical properties of the world, have been compiled into the visual system. The paper also examines a number of examples where instructions and "hints" are alleged to affect

Abstract:   In this paper we focus on the modularity of visual functions in the human visual cortex, that is, the specific problems that the visual system must solve in order to achieve recognition of objects and visual space. The computational theory of early visual functions is briefly reviewed and is then used as a basis for suggesting computational constraints on the higher-level visual computations. The remainder of the paper presents neurological evidence for the existence of two visual systems in man, one specialized for spatial vision and the other for object vision. We show further clinical evidence for the computational hypothesis that these two systems consist of several visual modules, some of which can be isolated on the basis of specific visual deficits which occur after lesions to selected areas in the visually responsive brain. We will provide examples of visual modules which solve information processing tasks that are mediated by specific anatomic areas. We will show that the clinical data from behavioral studies of monkeys (Ungerleider and Mishkin 1984) supports the distinction between two visual systems in monkeys, the what system, involved in object vision, and the where system, involved in spatial vision